Questions on Chapter 5
Ying Zhang
Question 1
• The efficiency of ALOHA
– When there are N active nodes the efficiency of
slotted ALOHA is Np(1-p)^{N-1}, find the value p
that maximizes the expression
– Using the value of p found in (a), find the
efficiency of slotted ALOHA by letting N approach
infinity.
solution
Maximum efficiency of pure ALOHA
• Show that the maximum efficiency of pure
ALOHA is 1/(2e)
solution
Question2
• Consider a broadcast channel with N nodes and a
transmission rate of R bps. Suppose the broadcast
channel uses polling for multiple access. Suppose
the amount of time from when a node completes
transmission until the subsequent node is
permitted to transmit(that is, the polling delay) is
t_poll. Suppose that within a polling round, a
given node is allowed to transmit at most
Q
bits. What is the maximum throughput of the
broadcast channel?
Question 3
• Consider three LANs interconnected by two
routers below.
• A) redraw the diagram to include the adapters
• B) Assign IP addresses to all of the interfaces.
For Subnet 1 use addresses of the form
111.111.111.xxx; for subnet 2 uses addresses
of the form 122.222.222.xxx; and for Subnet 3
use addresses of the form 133.133.133.xxx
• c) assign MAC addresses to all the adapters
• D. consider sending an IP datagram from Host
A to Host F. Suppose all of the ARP tables are
up to date. Enumerate all the steps as done
for the single router example
router
router
subnet2